Verity Rushworth says it was "very emotional" when Donna Dingle told Marlon she has cancer.
The actress - who left the soap in 2009 before returning last month - admitted she and her co-star Mark Charnock found the scenes difficult to film.
She told What's On TV: "That was a heavily emotional day. In the space of one episode, Marlon and Donna go from shock, through to anger and then the emotion comes out. I really poured my heart and soul into it."
Mark agreed the scenes were "upsetting" and "affected" him, even though he knew he was playing the part of a character.
He admitted: "It was upsetting. I am not a method actor, but you can't help but be affected by a story like this, especially when you see April who looks like a little Verity.
"It also felt like such a big responsibility. I wanted to get it right because this happens to people."
However, he still uses his own "sad" experiences to help his performance - and the bond the two actors share helped make the moment more real.
He added: "It really helps that I have a bond with Verity. We get on really well, so it is easier to access that chemistry.
"I like a laugh and a joke on set, but when I am doing scenes like that, I can't do that or else I lose the 'truth' of what Marlon is feeling. I do prepare myself by thinking of sad things that have happened to me."

Chloe Sims wants to "settle down".
The reality TV star has opened up about her first date with Elliott Wright, and even revealed she thinks they "could be together forever".
She told OK! magazine: "I really opened up and told him where I thought I'd be at this age - settled down.
"He knew I really liked him at that point. He really opened up too. It was really romantic ... We might be together forever - if he plays his cards right!"
Meanwhile, it appears Elliot - who, like Chloe, has a child from a previous relationship - it also ready to settle down, hinting he would be willing to if he "met the right girl", before suggesting the 'TOWIE' beauty could be the one.
He said: "I'd get married again if I met the right girl. Marriage is a beautiful thing.
"Would I have kids again? Yes ... I said ['I love you'] to her in a very romantic state and said that if I was to fall in love again it would be with someone like Chloe."

Rhod Gilbert has been confirmed as the new host of 'Never Mind The Buzzcocks'.
The 45-year-old comedian - who has presented the humorous music quiz show in the past - will become the programme's new front man for its next series as he joins regulars Noel Fielding and Phill Jupitus on the panel.
He joked: "After my first 'Buzzcocks' in 2009, I was told I was in with a shout to take over as regular host, and now, just five years later, I got the call. It has all happened so fast.
"'Never Mind The Buzzcocks' is one of those rare shows that feels like it belongs on our screens - it's an institution, in a good way.
"It's a great honour to be asked to take the reins full time and to hang out with Noel and Phill, and I'm equally excited and nervous about adding my name to those who have hosted it in the past."
Rhod will become the first regular presenter since 2009 when he takes over this autumn, with the show featuring guest hosts for the last five years.
Mark Linsey - BBC's controller of entertainment commissioning - described the comedian as "the perfect" fit.
He said: "Rhod is the perfect host for Buzzcocks. He has great knowledge of music and fantastic comedy talent that will brilliantly complement Noel and Phill."

Andy Serkis has never been uncomfortable with his face not being seen on screen.
The Hollywood star has become a pioneer for motion-capturing technology - initially through his roles in 'The Lord of the Rings' and 'The Hobbit' trilogies - and he has no problem with appearing as something unrecognisable in the likes of 'Dawn of the Planet of the Apes'.
He told the Wall Street Journal: "I was never not comfortable with it, I have to say. What I've always loved about acting was the transformative [sic] experience.
"And when I started of as a theatre actor before I got into film at all... for me it was about ... using myself, but being able to say something about the human condition, the further away I got from myself."
Andy first got his proper introduction to the technique when he took on the digitally-enhanced role of Gollum in 'The Lord of the Rings', and he fell in love with it as a branch of filmmaking.
He added: "Using performance capture technology for me - I stumped across it during when we were creating Gollum for 'The Lord of the Rings'.
"As a process, as a way of bringing characters to life, I absolutely adore it."

Sigourney Weaver has revealed her on-screen son will become a Ghostbuster in the next sequel.
The third installment in the spooky supernatural comedy is being made, and the actress - who played musician Dana Barrett in the first two movies - admitted she only had one request for producer Ivan Reitman before agreeing to return.
She told Vanity Fair magazine: "I said, I have one condition want my son Oscar [from 'Ghostbusters II'] to be a Ghostbuster, and he said, 'We've already done that.' "
The new movie has been rumoured and in various stages of productions for years now, and it is expected to feature a new generation of Ghostbusters, with the original cast making cameo appearances.
Of the original team, only Ernie Hudson and Dan Aykroyd are confirmed to return, following the tragic death of Harold Ramis earlier this year.
Meanwhile, Bill Murray is yet to say for definite whether he will make a return or not - but writer Etan Cohen insisted while he would be missed, the film could still work without him.
He said: "Absolutely everyone wants Bill Murray. But everyone has great faith in the franchise."

Katie Price believes sex should be "spontaneous" and has urged couples not to censor their love lives.
The former glamour model insists people shouldn't limit themselves to lovemaking in the bedroom and should get frisky wherever the mood takes them.
Katie - who once starred in a sex tape with ex-boyfriend Dane Bowers - said: "One thing that ruins sex is that people always think about it when you go to bed at night, you're in bed and that's when you have sex. I hate that as well. I think bed is for sleeping, not just for sex.
"So be spontaneous: go outside or do it somewhere different in the house. So many couples think, 'OK we're in bed, now we can have sex.' "
Katie is currently pregnant with her fifth child, her second with estranged husband Kieran Hayler, and accepts you can't be sexually adventurous when you're pregnant because the bump can make things awkward.
Speaking during her Fubar Radio show, she added: "When you've got a bump, you can't be as adventurous - well you certainly don't want to do it in front of the mirror, for one. And you can't because the bump gets in the way."
Despite giving birth four times to Harvey, 12, Junior, nine, Princess Tiaamii, seven, and 11-month-old Jett, Katie never realised why sex can help to bring on labour.
The 36-year-old beauty said: "I only just found this out myself. They say that if your baby's late or you want to bring on the labour, they say go and have sex.
"But it's not the sex that brings on the labour, it's the man's sperm. I always thought, 'Is it the sex? The bang, bang, bang, breaking it.' And it's not, it's the actual sperm. It gives off a hormone. That's what triggers it off."

Nicole Richie takes "responsibility" for Benji Madden and Cameron Diaz getting together.
The 32-year-old socialite - who is married to the Good Charlotte rocker's twin brother Joel Madden - "approves" of the couple's new relationship and admitted she was the one who got them together.
Asked on 'Watch What Happens Live' if she set them up, she said: "Yes. I'm going to take responsibility for everything!"
Nicole - who has children Harlow, six, and Sparrow, four, with Joel - is delighted her brother-in-law has found happiness with the 'Sex Tape' actress in recent months.
She added: "I approve of anything that's going to make Benj happy.
"I am a devoted sister in law. I'm happy for anyone who is happy, and I want everyone to be surrounded with love."
It was previously claimed that 35-year-old Benji is "madly in love" with the 41-year-old actress, but she doesn't want to rush into anything serious.
A source said recently: "Benji is madly in love with Cameron, but she wants to take it slow -- he isn't her usual type. He has dated a lot of Nicole's friends in the past but Nicole really wants this one to work."

Mila Kunis' first kiss was with Ashton Kutcher.
The 30-year-old actress shot to fame starring on 'That 70's Show' with her now-fiance and she is delighted that some of her teenage milestones were marked with the hunky actor, even if they were only on screen.
She told the new issue of W magazine: "My first real kiss ever was with him on the show...and when 'That 70's Show' had a prom, my date for the prom turned out to be my fiancé. We can honestly say we went to prom together!"
The 'Friends with Benefits' star previously admitted she never wanted to get married until she fell for Ashton.
She said: "I never wanted to get married. From the age of 12, I prepared my parents for no marriage. Then things changed - I found the love of my life."
The couple are expecting their first child - a baby girl - together in October and Mila has admitted she will be putting her career on hold to be a full-time mother.
She said: "I have never wanted to be the person who only has business on her mind. To me, this job has always been a hobby that turned into a great profession, but I don't eat and breathe acting."
Ashton began dating the brunette beauty in 2012 following his split from his first wife Demi Moore in 2011.
The former couple's divorce was finalised last November and Ashton popped the question to Mila a few months later.

Pamela Anderson has written a poem about her heartbreak.
The 'Baywatch' favourite posted a cryptic stream of consciousness piece on her Facebook page after news broke that she was divorcing Rick Salomon for the second time, just six months into their marriage.
The lengthy first-person essay, posted yesterday (08.07.14) but dated July 1, 2014, sees a confused Pamela put her feelings in writing about the unrealistic notion of holy matrimony and failing to find happiness despite her best efforts.
She mused: "Our true character, collective complexities. / childish activities - / patterns- genetics? Attention deficit- /- ...SEX ... a lost art- a sickness- / Perversions- / Lost sensuality - The cruel smell of orange blossoms.../ I love being in love- but expectations, / make it impossible to be happy- / or satisfied... / I've tried... so hard.. / maybe it's not in fashion- / Tradition...just seemed so romantic..., / I guess it's a used up ideal - for the old fashion.../ not modern."
Pamela, 47, seems to imply infidelity when she paints a picture of a "secret life", slipping out of a hotel room in the early hours of the morning.
She writes: "What have I done...? /I knew it was wrong from the start- / primitive- base instinct.."
The actress - who first married Rick in October 2007 before having their union annulled in February 2008, and announced earlier this year she had secretly remarried the poker player - proves herself to be an experimental writer, employing tactics like an external narrator, who she describes as "a deep voiced sexy black guy" to help tell her story.
Pamela - who was also previously married to Tommy Lee, the father of her two sons, and Kid Rock - blames herself for the breakdown of her union and the feeling of "discontent" that spoiled the couple's "obsessive love".
She rages: "o frustrated- / burning... questions.../ No man knows what to do with me- /I blame myself".
The poem was well received by her fans, who were amazed by her creative genius and pledged their undying love for her.
One wrote: "Wow...you are as intelligent as you are beautiful. You were wasted on all the men you loved... Wasted."

Kim Kardashian was spotted enjoying the fairground rides in Jersey Shore, New Jersey. The reality TV star was joined by her pal Jonathan Cheban as she rode the swings and a tandem bicycle.

Rihanna turned heads in a pink nightgown inspired dress teamed with converse trainers and a denim jacket as she left an office building in Midtown, New York City.

Halle Berry looked stunning in cream as she arrived for an appearance on CBS' 'This Morning' at their New York studios. The actress finished off her look with a pair of nude heels.